This invention relates to an improved procedure and apparatus for introducing liquids within a thermoplastic or thermoset production system. Such an inventive apparatus comprises a storage tank for the desired liquid, a device which connects to a flow channel (such as a manifold or pipe) through which the target thermoplastic or thermoset composition is flowing, and a transfer line connecting the storage tank with the connecting device. The connecting device itself easily attaches and detaches to the flow channel through a spring-loaded or sliding-lock mechanism. Such a novel apparatus permits an ease in changeover from one liquid to another without the need for time-consuming cleaning and without complicated shut-off, removal, and replacement steps. Furthermore, such an apparatus allows for quick start-up, a drastic reduction in time required for changeover, and, with the connecting device being attached directly to the flow channel, a reduction in potential clogging through the unwanted misdirection of thermoplastic or thermoset composition into the connecting device and/or transfer line itself. As noted above, the particular procedure for producing such thermoplastic or thermoset compositions through utilization of such an apparatus is encompassed within this invention as well.
Thermoplastic and thermoset products are utilized to provide different articles and for myriad purposes. For instance, polyester thermoplastic articles include soft drink bottles, medicine vials, and the like; polyolefin thermoplastic articles include food containers, films, and the like; polyurethane thermosets include, without limitation, slabstock foams, carpet underlays, surface coatings, and the like. In order to produce such articles, it is necessary to heat-melt the base thermoplastic to a liquid or otherwise process a thermoset into which any number of additives may be present, or, more particularly, incorporated therein. Such additives could include antioxidants, nucleating agents, plasticizers, acid scavengers, brighteners, and, most preferably, coloring agents.
With the desire for certain aesthetic qualities within the marketplace for such products, the addition of colorants within such thermoplastics or thermosets has become commonplace. As noted above, the introduction of such coloring agents within target thermoplastics is generally performed through a pipe (or similar channel) attached simultaneously to both a coloring agent storage tank and the flow channel (pipe, etc.) within which the plastic pellets are transported. Unfortunately, such a configuration has proven difficult in the past, particularly since such apparati are attached through extensive connecting devices (clamps, screws, seals, etc.) to the target plastic flow channel. Furthermore, the feed lines from the coloring agent storage tanks have not been connected adjacent to the flow channel itself; in general, such a connection from the storage tank is present on a separate shunt pipe located on the flow channel itself. Thus, the shunt pipe is the component through which the coloring agent must penultimately travel through prior to introduction within the target plastic within the flow channel. In such a configuration, the shunt pipe is susceptible to clogging, requires cleaning after use (particularly prior to utilization of a different coloring agent through the same shunt pipe), all of which adds inordinate amounts of time to the already time-consuming procedure. As a result, there is a need to provide a liquid metering device for such procedures which foregoes such cleaning requirements, reduces the chances for clogging of coloring agent and/or molten plastic within the feed line itself, and thus, which provides a more efficient manner for changing coloring agents (and other liquid additives) during plastic production. To date, there have been no such specific developments to such a degree within the pertinent thermoplastic or thermoset production industry.
Such an introduction of such coloring agents within such target plastics has, as alluded to above, through rather cumbersome procedures. For instance, such methods of introduction have been met in the past through the utilization and introduction of colorants through one or more pipes or injectors, arranged consecutively and serially (if a plurality is present), through connections (feed lines, etc.) feeding to a manifold, and ultimately onto and/or mixed with pellets or into molten plastic formulations. The pipes or valve assemblies have been disposed in the past by merely creating a hole in the manifold to which the pipe or valve assembly is attached. The colorant would then be fed (by pressure or gravity, for instance) through the pipe or valve assembly and emptied into the pellet or molten plastic stream travelling through the manifold. These colored mixtures are then generally fed to a further mixing vessel or, in the instance where pellets are colored, to a melting vessel (such a heated screw, and the like) and fed to the desired molder, extruder, etc. Such a standard method has proven inefficient and problematic in the past since the utilization of a feeder pipe into the flow channel manifold requires a number of extra, time-consuming procedures upon changeover from one coloring agent to another. For example, the feeder pipe must be cleaned of excess coloring agent; the target plastic (be it in pellet or molten form) may enter such a feeder pipe instead of the flow channel manifold (thereby creating potential clogging, flow, and/or waste problems; and instantaneous shut-off and, more importantly, start-up are nearly impossible to accomplish. Furthermore, the connection between the coloring agent storage tank and the coloring agent feed line (directly attached to the plastic flow channel manifold) is generally made by a rigid or flexible tube which is attached to the feed line, at least, through a cumbersome, rather reliable, device (such as a clamp) wherein the tube is generally larger in diameter than the feed pipeline. Thus, even flow problems and leak possibilities are increased, and in fact, prevalent, with such a standard traditional configuration. Therefore, it is evident that improvements are highly desired within the industry to permit more efficient and effective introduction of liquid additives within thermoplastic or thermoset formulations and articles.
In the past, custom blends of coloring agents, such as polymeric colorants, were prepared prior to use by mixing two or more xe2x80x9cprimaryxe2x80x9d colors prior to incorporation within the target plastic. The components would be mixed together using some type of agitator such as a mixer or a drum tumbler. Once the blend was of an appropriate shade it was transferred to a storage tank for further introduction within the foam substrate. Upon completion of coloring with a specific batch of polymeric colorant, the previously run color would have to be emptied from the storage tank; the tank would need to be cleaned; and then the next color to be run in the same tank would have to be charged in the tank. Cleaning of the tanks, feed lines (a.k.a. pipelines), etc., was facilitated due to the water-solubility of the polymeric colorants (particularly as compared to pigments); however, the procedures followed were still considered labor intensive and not cost efficient. The general practice was then modified to maintain a dedicated tank for each separate color (shade) that was to run. This led to a number of inefficiencies and limitations that were not desirable if a foam or thermoplastic manufacturer was to adequately meet demands in the market place.
Polymeric colorants, such as disclosed in U.S. Pat. No. 4,284,729 to Cross et al., herein entirely incorporated by reference, were designed to be totally miscible with one another as well as within most plastic components (such as polyols, one of the two main ingredients used to produce polyurethane materials, isocyanates being the other, for example). Pigment dispersions, on the other hand, are particulates dispersed in some type of liquid carrier. They require a high degree of agitation before they satisfactorily blend together to provide a uniform color. Furthermore, they are generally not water-soluble and thus either difficult to clean from certain surfaces or, alternatively, require the utilization of undesirable organic solvents (methylene chloride, and the like, for example) for removal. Additionally, colorants such as acid dyes, solvent dyes, and the like, are also utilizaed for the coloring of thermoplastics and thermosets which also tend to pose the same general cleaning problems and miscibility difficulties as pigments. However, the inventive metering device may be utilized in conjunction with any of these types of coloring agents for introduction within the target plastic formulations.
Also, the liquids to be introduced within such plastics are not limited to coloring agents (although such compounds are preferred). As a result, any liquid additives added within plastics may be utilized with such an inventive system. Included, without limitation, within the list of additives are clarifying and/or nucleating agents (as in U.S. Pat. Nos. 6,102,999 and 6,127,470 to Cobb, III et al., both herein entirely incorporated by reference), plasticizers, optical brighteners, antioxidants, acid scavengers, and the like.
It is thus an object of the invention to provide a new, easy to use, configuration of a liquid metering device for the introduction of liquid additives onto a plastic pellets. As well, such an object includes the introduction of liquid additives into molten plastics with the same easy-to-use device. A further object of the invention is to provide a liquid metering device which drastically reduces the possibility of clogging within a feed pipeline from the liquid storage tank to the target plastic manifold flow channel. Another object of this invention is to provide an easy-to-remove and/or attach feed line for introduction of liquid additives to target plastic formulations within a manifold flow channel.
Procedures for the coloration of plastics is set forth in U.S. Pat. No. 4,640,690, to Baumgartner et al., and U.S. Pat. No. 4,507,407, to Kluger et al., both entirely incorporated herein by reference, in which liquid polymeric colorants are added to the resin before or during compounding and polymeric addition reaction. These patents also provide the same definition and scope of the terms xe2x80x9cthermoplasticsxe2x80x9d and xe2x80x9cthermosetsxe2x80x9d as for the inventive coloring applications. The term xe2x80x9cplasticxe2x80x9d is herein intended to encompass both thermoplastic and thermoset compositions and articles.